In Society of Automotive Engineers (SAE) paper 930650, "A Complete Frontal Crash Sensor System--I", by Breed et al, which is included herein by reference, the authors conclude that airbag crash sensors mounted in the crush zone are necessary for the proper sensing of airbag required crashes. They also conclude that such sensors should sense crashes to all portions of the front of the vehicle and that sensors which sense the crush of the vehicle are preferred. The theory of crush sensing is presented in the co-pending U.S. patent applications cross referenced above and in SAE paper No. 920122, "Performance of a Crush Sensor for Use with Automotive Airbag Systems", by Breed et al, which are both included herein by reference.
The tape switch crush sensor described in the above referenced co-pending patent application, has performed successfully on various staged vehicle crashes into barriers and poles. These sensors are line sensors and will sense any crash which results in a deformation in the area where the sensor is mounted. Research has determined that at least three such sensors are required to sense all crashes involving the front of the vehicle inside of the rail structures. Additional sensors are required if crashes outside the rails are to be sensed in time. Although these sensors perform better than the standard ball-in-tube or spring mass sensors, it would be better yet if a single sensor could sense all airbag desired crashes involving the front of the vehicle.
Other SAE papers which provide pertinent background information to this invention include:
1. Breed, D. S., Sanders, W. T. and Castelli, V. "A Critique of Single Point Crash Sensing", Society of Automotive Engineers No. 920124, 1992. PA1 2. Breed, D. S., Castelli, V. and Shokoohi, F. "Are Barrier Crashes Sufficient for Evaluating Air Bag Sensor Performance?", Society of Automotive Engineers No. 900548, 1990. PA1 3. Shokoohi, F., Sanders, W. T., Castelli, V., and Breed, D. S. "Cross Axis Specifications For Crash Sensors", Automotive Technologies International Report, ATI 12004, 1991. Society of Automotive Engineers No. 930651, 1993. PA1 4. Breed, D. S., Castelli, V. "Problems in Design and Engineering of Air Bag Systems", Society of Automotive Engineers No. 880724, 1988. PA1 5. Breed, D. S., Castelli, V. "Trends in Sensing Frontal Impacts", Society of Automotive Engineers No. 890750, 1989. PA1 1) To provide a single sensor which will sense all airbag desired crashes involving the front of the vehicle. PA1 2) To provide a sensor which is much longer than it is wide or thick thus permitting it to sense crashes over a large area while occupying a small space. PA1 3) To provide a sensor which can be easily shaped so to be properly placed relative to the crush zone boundary across the entire front of the vehicle. PA1 4) To provide a sensor which will sense a low pole impact which engages the vehicle below the bumper. PA1 5) To provide a sensor which will sense an impact to the vehicle outside of the vehicle supporting structure, such as the rails. PA1 6) To provide a crush sensor where the deformation required to trigger the sensor can be varied along the length of the sensor. PA1 7) To provide a sensor to be used along with an electronic passenger compartment sensor which will trigger on all of the airbag desired crashes which are missed by the electronic passenger compartment mounted sensor. PA1 8) To provide the simplest sensor system consisting of a single discriminating sensor mounted in the crush zone and a single arming sensor mounted in the passenger compartment. PA1 9) To provide a crush zone mounted sensor which will not cause the airbag to deploy on low velocity change impacts into animals. PA1 10) To provide a crush sensor which is not easily damaged during routine maintenance or normal environmental influences during the life of the vehicle. PA1 11) To provide a sensor which remains closed after it triggers during a crash. PA1 12) To provide an hermetically sealed crush zone mounted crash sensor. PA1 13) To provide a sensor which cannot be reused after it has been involved in a crash where the airbag deployed. PA1 14) To provide a crash sensor which has an integral connector thereby eliminating the need for wires to be connected inside the sensor housing. PA1 15) To provide an hermetically sealed sensor which is easily assembled and does not require glass-to-metal seals.
Other relevant prior art includes U.S. Pat. No. 3,859,482 to Matsui. Matsui discloses various devices which respond to the pressure which accompanies a vehicle crash when material crushed in the extreme front of the vehicle impacts the pressure detecting device. His devices discriminate crashes based on the magnitude of this pressure on the detecting device. His devices are placed far forward in the vehicle where they are in the front of the crush zone at the time that sensor triggering is required.
The devices disclosed in this invention, on the other hand, are usually mounted at the extreme rear of the crush zone at the time that the sensor is required to trigger and respond to the amount of crush of the vehicle as taught in U.S. Pat. No. 4,995,639 to Breed. Thus, it is mainly the distance that the crush zone had propagated into the vehicle that is sensed rather than the amount of force on the sensor as in Matsui. Devices disclosed in Matsui are very poor at discriminating airbag desired crashes from those where an airbag is not required since a localized force is sufficient to trigger the sensor. As taught in the above references, a crush sensing sensor must be located at the boundary of the crush zone at the time that deployment is required. In addition to the location of the sensor, there are many structural differences between the devices disclosed in Matsui and here.